1992: Fault-Tolerance Software

Traditionally, large-scale, complex telephone switching operations have used
mainframes to ensure the reliability of telecommunications systems. But in
1992, an AT&T team developed a software alternative to large
mainframe backups. For example, fault tolerance software detects faults that
threaten to shut down a switching system which allots calls to individual
phones, and takes corrective action to keep the switching system running.

Much like a dose of cough suppressant to an aching human, fault tolerance
software allows a telecommunications system to "tolerate" hardware faults, and
some of the design and coding faults built into them. The cough or bug may not
be completely cured, but the system can still function effectively. Fault
tolerance software detects faults that are, for example, about to shut down a
switching system that is allotting calls to individual phones, and takes
corrective action. Easily embedded in any application, this vigilant software
detects failures, backs up and recovers data, eases communications among
processes, copies key files for backup, and automatically restarts and
restores crashed programs in seconds. In addition to telecommunications, fault
tolerance software can be found in a number of systems where avoiding service
outages is crucial, such as on Wall Street and in automatic teller machines.